rust protover_all_supported() accepts too-long protocol names
[569b4e57e23d728969a12751afc6b45f32d0f093](https://gitweb.torproject.org/tor.git/commit/?id=569b4e57e23d728969a12751afc6b45f32d0f093) was fixing legacy/trac#25517 but kept the old behavior of allowing protocol names of any length for `protover_all_supported()`. That's the reason [this unit test was failing, and ended up being disabled on rust builds](https://gitweb.torproject.org/tor.git/commit/?id=a5d4ce2b393955f60962d3db8744a846506c3e7b) with a ??? comment of confusion. The reason given in the commit for this behavior was `in order to maintain compatibility with consensus methods older than 29.` but the corresponding [C code change](https://gitweb.torproject.org/tor.git/commit/?id=eb966928428a80c105d33bd60bcae5503a1adeb7) never made any exception like this. **Trac**: **Username**: cyberpunks
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